As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE UPPER PORTION OF THE REAR DOOR OPENED IN-FLIGHT AFTER STARTING DESCENT. THE DOORS WERE POSITIVELY CLOSED PRIOR TO START OF FLIGHT. INSPECTION FOUND THE NUT CHANNEL TO HAVE FALLEN OFF THE DOOR FRAME ALOWING THE DOOR TO OPEN PART WAY.